This invention relates to manual data collection and specifically to a data collection apparatus for identifying who the creator is, for identifying what the creator is doing in the form of information input, and/or for determining the neuromuscular condition of the creator. This invention relates specifically to the art of xy position and pressure recognition and information input through a stylus or similar writing instrument.
In the past, two separate technologies have developed using a stylus for data input of some form. In the first technology, techniques have been developed for recognizing xy position of a stylus on a surface. Into this class of technology fall the digitizer pads which interact with a stylus of some form to sense position of the stylus in two dimensions at the surface of the pad.
In the other technology, art has developed for tracking movement and/or forces to which a stylus is exposed. This latter technology has been used primarily for signature verification and recognition but not for data input because data input is relatively inaccurate when attempts are made to translate the information gathered through a stylus into the xy position information needed to decipher characters and the like. More specifically, it has been determined that it is virtually impossible to identify true position of a stylus on a surface derived solely from force information from a stylus because of, among other things, the interaction of forces between the stylus and the writing surface, the orientation of the stylus relative to the writing surface, including roll, pitch and yaw positioning, and the positioning of sensors within the stylus. Hence, the use of stylae has been more or less discounted as a means for pure data entry.
On the other hand, a stylus is very useful for certain classes of signature verification. For example, the automatic signature verification system using a three axis force-sensitive pen developed by one of the co-inventors of the present invention with others has been found to be a very effective tool for signature verification. The subject matter of an article published under the title "Automatic Signature Verification Using a Three-Axis Force-Sensitive Pen," IEEE Transactions on Systems, Man & Cybernetics, Volume SME-13, No. 3, pp. 329-337 (May/June 1983) is incorporated herein by reference and made a part hereof. This article describes a three-axis force-sensitive pen used in connection with the present invention. It also describes a method for processing signals extracted from the transducers of the force-sensitive pen.
One of the features of this prior art pen, previously recognized as useful to signature verification, is its ability to sense force at the point of the stylus on a writing surface. While inherent in the structure of the pen, the usefulness of this feature has not been recognized in other applications discussed herein, although this pen has been under development and known to the art for more than a decade. For example, attempts have been made to use such a pen for data entry and found to be inadequate to the point where a project to use such a pen for data entry was abandoned. Reference is made to the article by Crane and others entitled "An On-Line Data Entry System for Hand-Printed Characters," published in March 1977 in Computer Magazine pp. 43 through 50. This paper is incorporated herein by reference and made a part hereof. This paper describes the actual physical attributes of the sensing mechanism of the pen and early attempts at use of this pen for character recognition. This project was subsequently abandoned as having limited practical usefulness. One of the reasons it was abandoned was that its use required the constraint that all users hold the pen in only one manner with respect to pitch, roll and yaw.
There are other signature verification systems known to the art which are based on stylus construction. Representative of the art are patents issued to Herbst, et al., U.S. Pat. No. 4,128,829, which mentions earlier work by Herbst and others. Early work by Herbst was based on a single acceleration parameter of a signature dynamic, whereas the subsequent Herbst patent describes multiple-axis acceleration parameters in conjunction with an axial force parameter through means of accelerometers and a strain gauge measuring force along the axis of the stylus. A subtle though important feature of this prior invention is that the accelerometers measure a force of acceleration at a point other than at the junction of the writing surface with the stylus. Hence, it is virtually impossible to obtain any information about positions, either absolute or relative, at the point of intersection of the stylus and the surface. Moreover, if acceleration were measurable at the point of intersection, it would be possible to obtain direct information about relative position of the point on the surface, although it is impossible to derive absolute position. Acceleration measured at that point would not be an indication of true position at the point of intersection of the stylus and the surface. The nature of this pen as actually constructed makes it impossible to even infer position at the point due to the lack of information about the nature of the interaction of the point of acceleration and the point of intersection of the stylus on the surface. The interaction of these two positions varies between subject or users.
Xy position tablets and the like are known wherein xy position is sensed in an absolute sense and z position, including force, may well be sensed on the surface of the tablet. In any case, the force so measured is derived from the downward force interaction between a stylus and a tablet. It is believed that none of these structures use the force at the tip for any reason other than sensing contact between the stylus and the surface.
An important reference is the article by H. D. Crane and J. S. Ostrem entitled "Automatic Signature Verification Using a Three-Axis Force-Sensitive Pen", IEEE Transactions on Systems, Man and Cybernetics, Vol. SMC-13, No. 3, May/June 1983, pp. 329-337. This reference describes, among other things, a preferred technique for recognizing a signature as a forgery. However, the technique described therein has only limited character recognition capabilities, because it could not sense position relative to a fixed reference position.
The following patents were identified in searches of the prior art:
U.S. Pat. No. 3,767,907 to Radcliffe, Jr. discloses a technique for achieving mathematical cross-correlation in which a stylus is used in connection with a strip of film in the stylus.
U.S. Pat. No. 3,906,444 to Crane et al describes a signature verification system using a stylus with four position outputs related to x-y position and a clock output.
U.S. Pat. No. 3,915,015 to Crane et al. describes a writing instrument which uses strain gauges and which is capable of sensing force at a tip. Circuitry is disclosed which is potentially useful in connection with the present invention.
U.S. Pat. No. 3,930,229 to Crane et al. describes a handwriting system using a stylus with four position outputs related to x-y position and circuitry wherein a set of digital signals are generated to identify a character.
U.S. Pat. No. 3,988,934 to Kamphoefner et al. describes a spatial sensing apparatus for handwriting analysis.
U.S. Pat. No. 4,040,010 to Crane et al. describes a method and system for identifying handwriting using x and y and pressure input.
U.S. Pat. No. 4,040,011 to Crane et al. describes a further system for identifying handwriting using x and y and pressure input.
U.S. Pat. No. 4,040,012 to Crane et al. describes a still further system for identifying handwriting using x and y and pressure input.
U.S. Pat. No. 4,078,226 to EerNisse et al. describes a stylus for use in signature verification which generates signals representative of force in response to writing pressures. A writing surface is provided therewith in which z force, that is up/down directional force only, is sensed in connection with the forces derived from the stylus.
U.S. Pat. No. 4,086,567 to Crane et al. describes a still further system for identifying handwriting using x and y and pressure input.
U.S. Pat. No. 4,122,435 to Greenaway describes a position sensor which at most senses contact force between the writing surface and the stylus.
U.S. Pat. No. 4,128,829 to Herbst et al. has been discussed above.
U.S. Pat. No. 4,190,820 to Crane et al. describes a still further system for identifying handwriting using x and y and pressure input.
U.S. Pat. No. 4,234,868 to Radice describes a signature verification device or like pattern verification device comprising a sheet of a piezoelectric-forming resin used for gathering information related to force orthogonal to a writing surface.
U.S. Pat. No. 4,240,065 to Howbrook describes a position sensing apparatus in connection with a surface wherein a coil mounted on a stylus is used to signal proximity of the stylus to the surface.
U.S. Pat. No. 4,281,313 to Boldridge, Jr. describes a position sensing apparatus built into a surface for the intention of recognizing signatures derived from pressure against the surface.
U.S. Pat. No. 4,475,235 to Graham describes a signature verification technique relying on position and downward force against a tablet.
U.S. Pat. No. 4,475,240 to Brogardh et al. describes a system built around an optical sensor for following precision information derived from markings produced by a stylus on a surface.
U.S. Pat. No. 4,495,644 to Parks et al. describes an apparatus for real-time signature verification which uses a transducer pad in which the pressure of a stylus causes contact to be made between two resistive films to sense x and y coordinate position information. The system is described as useful for both signature verification and character recognition.
UK Patent Application GB 2,039,118A of Standard Telephone describes a signature recognition system based on a waveform identification technique verification.
Work at SRI International of Menlo Park, California, by one of the co-inventors and others is discussed in the above-mentioned papers co-authored by Crane and patents issued to Crane with others.